E2E Test log should capture output from helm-test

[jlewi]

We should capture the output of helm-test in the build log created by runner.py.

Here's an example build log
).

The relevant lines are

Running: /go/bin/helm-test --image=gcr.io/mlkube-testing/tf_operator:v20171029-29b5d3e --output_dir=/tmp/tmpTfCrdTestHhjiY8 
cwd=None
Subprocess output:

helm-test failed; Command '['/go/bin/helm-test', u'--image=gcr.io/mlkube-testing/tf_operator:v20171029-29b5d3e', '--output_dir=/tmp/tmpTfCrdTestHhjiY8']' returned non-zero exit status 2
Running: ./lint.sh 

So no output is captured from helm test.

[jlewi]

helm-test writes most of its output to the junit-01.xml file. There are some log statements at info level but those are probably missed because we haven't set the logging level to include them.

[jlewi]

Here's the output, helm-test.output.txt, from running

~/go/bin/helm-test --image=gcr.io/mlkube-testing/tf_operator:v20171029-29b5d3e --output_dir=/tmp/tmpTfCrdTestHhjiY8 

So clearly we are missing a lot of output.

[jlewi]

I think the problem is that helm-test ends up writing to stderr and the functions in util.py are only capturing output from stdout and not stderr.

[jlewi]

This was fixed by #97